Two-stage preparation of soap thickener for hydrocarbon



1960 F. N. BAUMGARTNER 2,922,300

TWO-STAGE PREPARATION OF SOAP THICKENER FOR HYDROCARBON Filed 001:. 22,- 1956 QMQQq 354a N M402 09 0m 0w 0v ON T l to 803? l T :0 BSEE LQIQET mmma muomm S mEm6E 93 5323538 Frederick N. Baumgartner Inventor TWO-STAGE PREPTION F SOAP THICKENER FOR HYDRDCARBDN "Frederick .N. Baumgartner, Plainfield, NJZ, assignor to Essa Research and Engineering Company, a corporation of Delaware Application October 22, 1956, Serial No. 617,665

9 Claims. (Cl. 260-414) This invention relates to a two-stage operation in the preparation of water-insoluble metal soaps and particularly to those useful as hydrocarbon oil thickeners for minimizing product degradation which sets in on com pletion of the reaction. More particularly, it deals with the formation of basic aluminum disoaps of fatty acids and an interruption in forming the disoaps prior to the completion of the reaction, e.g. when the saponification is less than about 95 complete and the reaction mixture has a pH of about 6 to 7, i.e., so that it is substantially neutral or not more than slightly acidic.

The soap thickeners are, in general, formed in aqueous solvents by the reaction between an alkali metal soap of a fatty acid and alum or aluminum compound, e.g. an aluminum salt. The aluminum soaps have been prepared by the reaction of C to C aliphatic carboxylic acids, fatty acids and naphthenic acids, such as, acetic, hexoic, caprylic, capric, lauric, oleic, myristic, palmitic, stearic and dimerized linoleic to form products comprising basic aluminum disoap with varying amounts of free fatty acid. The disoap may have about 1.5 to 2 acid molecules per aluminum atom. Such soaps have value for gelling and thickening various hydrocarbon and organic liquids, e.g. naphtha, kerosene, heating oil, lubrieating oil, mixed distillates and halogenated hydrocarbons. The term alum is used as the equivalent of the aluminum compound reactants.

The aluminum soaps may be prepared by several different procedures. A conventional procedure for preparation of the aluminum soaps involves addition of aqueous solution of the aluminum salts, e.g. sulfate, halide, acetate, etc. to solutions of alkali metal soaps of the fatty acids in the presence of excess alkali, the excess alkali referring to the amount of alkali, e.g. sodium hydroxide, over the amount required for saponification of the fatty acid, represented by RCOOH.

In the normal or conventional procedure, the alum, or aluminum salt solution, is added to the solution of the alkali metal soap of the fatty acid at a controlled rate with stirring to precipitate the aluminum soap and at the completion of the alum addition there is a digestion period for completing the reaction. Another procedure, named for simplicity, the two-stream procedure, supplies the excess alkali cocurrently with the alum solution. In a reverse procedure the sodium soap solution is added to the alum solution. There are still fur ther modifications which can be made to obtain certain desired results. The conventional and the two-stream procedures are further described in U.S. patent application, SN. 617,654, concurrently filed October 22, 1956, by F. N. Baumgartner, said application being particularly concerned with the invention of the two-stream procedure claimed therein.

In various procedures of forming the disoaps, after completion of the admixing of the determined amounts of reactants, e.g. aluminum compound, fatty acid and alkali, an additional period of time for reaction, which may be called a digestion period, is usually required.

States atom It has been found that in adding final amounts of the alum solution, during the digestion period and any subsequent holding-period, a deterioration of the product tends to occur. This deterioration may be ascribed to hydrolysis, which tends to occur principally as the reaction mixture becomes acidic, i.e., has a pH going below 7, and this becomes more pronounced as the pH goes below 5.

During the preparation of the soap thickeners, it has been generally and frequently necessary to allow the precipitated soap to remain in contact with acidic aqueous mother liquor for an extended period of time, during which degradation of the final products tends 'to set in. Unfortunately, the extended holding period is frequently necessitated by lack of filter capacity or a slow-up of filtration. The problem of degradation from long digestion and holdup is 'solved to a'significant extent by using the two-stage procedure of the present invention by which digestion is carried out mostly under practically neutral conditions.

According to the present invention, degradation is further minimized if the main reaction is interrupted at below about 95% completion and at a point where the pH of the reaction mixture is above 5 and preferably about 6 to 7. This interruption may be in the two-stream procedure at a point where to of the theoretical amount of alum required has been added. The completion of the reaction is then carried out in a second stage. This interruption of the reaction prior to completion is applicable to theconventional, the two-stream, and other types of procedures if the soapis left in a mother liquor which becomes acidic on completing the reaction.

After the first stage is finished, i.e. on "the interruption, the reaction mixture is held preferably at a pH in the range of 6 to 7 for the necessary time to minimize degradation. Then, anadditional amount of alum or aluminum salt needed can be added for completion of the reactionin the second sage directly prior to filtration, washing and drying. In this manner, .a large batch of partially finished soap productrmay be prepared, then enough of the partially finished ,product may be withdrawn to an auxiliary smaller reactor for finishing of the reaction, as by digestion with the final required amount of alum or aluminum salt-added to obtain the batch for one filter run. The-entire contents of the finished batch can be filtered within a few minutes. In using an auxiliary reactor withdrawal of batches to the smaller reac- EXAMPLE 1 Conventional procedure Reactants:

Z-ethyl hexoic acid moles 3 NaOH o 4.5

H 0 grams 4392 Alum solution:

Al (SO -18H O moles 0.86 H O grams-.. 1560 Using the conventional procedure, the required amount of sodium hydroxide solution sufiicient to saponify the fattty acid and provide the desired excess of sodium hy- 3 droxide was mixed with the fatty acid and with the water. While stirring the mixture and maintaining the temperature at about 42 C. the alum solution was added slowly. A pH meter was used to'determine changes in pH of the solution as the alum was added, finally after all the alum had been added, and during the digestion The alum solution and the excess alkali hydroxide solution were added in separate streams cocurrently to the solution of the fatty acid soap which was made up to contain substantially no excess hydroxide. A pH meter was used to determine the changes in pH of the solution until the alum solution and the excess hydroxide solution had been completely added, then further during the digestion period. The rates of addition of the alum and the excess alkali were regulated to maintain the pH of the reaction mixture at approximately 7 until all of the excess alkali had been added.

The overall reaction in forming the basic disoap is represented by the following equation:

In the reaction, the sulfate radical may be replaced by other anions, e.g., halides, etc. In this reaction the acidity of the reaction mixture or the mother liquor in which the dibasic disoap is formed becomes more and more acid as the aluminum salt solution is added and reacted. When all the reactants have been mixed the reaction mixture generally has to be stirred for an additional few minutes for the completion of the reaction. Following completion of the reaction the reaction mixture product is subjected to filtration with any suitable means, such as a basket centrifuge, Biichner vacuum filter, etc., and the filter cake then is washed with water and finally dried at temperatures of the order of 40 to 50 C.

The present invention concerned with the final part of reaction prior to the filtration permits the partially formed reaction product to be produced continuously or in large batches, then maintained during the holding period at a pH above 5 and preferably in the range of 6 to 7 so that any portion of the thus formed product can be subjected in a smaller batch to a more expeditious finishing, e.g. by addition of the final required amount of aluminum salt reactant and digestion and thus providing a smaller batch of finished reaction product that can be more conveniently filtered at a rapid rate thereby substantially reducing the time that the precipitated soap is in contact with a final acidic mother liquor.

In the accompanying drawing, are illustrated typical titration curves obtained from the procedures of Examples l and 2. The curves show that when the amount of alum added is in the region of about 60 to 95% of the theoretical requirement, the pH of the reaction mixture is above 5 and'preferably in the range of 6 to 7. The two-stream procedure permits the addition of the alum to be closer to 95% before the reaction mixture becomes strongly acidic, i.e. drop of the pH below 5 toward 3.5.

- to contain 1% of 2-ethyl hexoic acid as peptizer.

It is to be noted that the interruption of the reaction for the present two-stage process may be made at close to mole percent addition of alum in the two-stream procedure and when somewhat less alum is added in the conventional procedure, e.g. 60 to 95%, to prevent the precipitated aluminum disoap from remaining in a strongly acidic reaction mixture mother liquor for a prolonged period after interruption of the reaction. The holding period which is the time between interruption of the reaction or disoap precipitation to the time that the reaction is again started for completion can be any substantial time adequate for permitting ready final separation of the disoap from the mother liquor of the reaction mixture, e.g. several minutes to se eral hours at moderate or ordinary temperatures, e.g. 15 to 40 C.

The following experimental data demonstrate and support the improved results of the invention:

EXAMPLE 3 Hydrocarbon gels were prepared according to a standardized procedure using a gasoline test liquid to be thickened. The 2 wt. percent soap containing gels were made The 1% gels contained 1% soap. The 1.2% gels contained 0.25% m-cresol. The gels, other than 2%, were aged at rom temperature. The 2% gels were aged at F. for 24: hours. The gels were tested for stability and gel consistency with a Gardner mobilometer, which measures the weight required to cause a perforated disc to pass a specific distance through a sample of the gel in a given time.

It will be noted that there is a significant improvement in results when the products are held under neutral or close to neutral conditions, rather than in an acid condition With a pH below 5 since the high Gardner values indicate better gel consistency.

Runs A and B were conventional type procedures. Runs C and D were two-stream type procedures.

It is to be understood that the present two-stage process applies to modifications of the two-stream and conventional procedures with provisions for carrying out precipitation of the basic aluminum disoap in a reaction mixture mother liquor at a pH above 5 and maintaining the pH above 5 by subsequent additions of alkali in a first stage so that the first stage product can be held for any desired period at a' pH above 5 until a final amount of aluminum salt is added to complete the reaction when the disoap can then be directly and quickly separated from resulting acidic mother liquor.

What is claimed is:

1. In the process of making a water-insoluble basic aluminum disoap that thickens a-hydrocarbon oil, the improvement which comprises forming the aluminum disoap to an incomplete stage in a liquid aqueous medium at below 95 completion of reaction, then holding said disoap in the aqueous liquid medium kept at a pH above 5 tominimize decomposition which the'disoap undergoes in the medium when it is more acidic, and holding the disoap in the liquidmedium at a pH above 5 for at least a few minutes prior to completion of reaction through final addition of aluminum salt which is reacted to form the disoap and gives said medium a pH below 5 on completion of the reaction.

2. In the preparation of a hydrocarbon thickener which is basic aluminum disoap of a C to C aliphatic carboxylic acid by reaction of an aluminum compound with an alkali metal soap of the aliphatic acid, the improvement which comprises interrupting the reaction of the aluminum compound with the alkali metal soap of the aliphatic acid when the resulting reaction mixture has a pH above 5, then holding the reaction mixture for at least several minutes at a pH above 5, and thereafter completing reaction in the reaction mixture by further adding said aluminum compound to said mixture whereupon the pH drops to below 5, then promptly separating the disoap from mother liquor of the reaction mixture.

3. A two-stage operation for preparing a hydrocarbon thickener which is a basic aluminum soap of aliphatic carboxylic acid, which comprises reacting an amount of an aluminum salt with alkali metal soap of C to C aliphatic carboxylic acid in a first stage to form an unfinished reaction product containing precipitated basic aluminum disoap in a mother liquor having a pH in the range of 5 to about 7, interrupting the reaction and holding the unfinished reaction mixture product at a pH above 5 for at least a few minutes except for a portion of the product which is to be separately finished, adding to the portion of the reaction mixture product which is to be separately finished sufiicient amount of the aluminum salt to complete the reaction including digestion at a pH below 5, and thereafter directly and rapidly separating the disoap from acidic mother liquor of the finished portion of the reaction product.

4. In the process of preparing a hydrocarbon oil thickener which is a basic aluminum disoap of an aliphatic acid, the improvement which comprises carrying out precipitation of the aluminum disoap by reaction of an aluminum compound with C to C aliphatic carboxylic acid of an alkali metal in an alkaline aqueous liquid medium until the reaction is from about 60 to 95% complete, with sufiicient alkali present to give the resulting reaction mixture at pH in the range of 6 to 7, then interrupting the reaction and holding the reaction mixture for at least several minutes at a pH in the range of about 6 to 7, thereafter finally completing the reaction by addition of more aluminum compound whereupon the pH of the reaction mixture goes to below 5.

5. In the preparation of a hydrocarbon thickener which is a basic aluminum disoap of a C to C fatty acid using a procedure in which an aluminum salt and excess alkali are cocurrently added to an aqueous solution of fatty acid soap of an alkali metal to precipitate the aluminum disoap, the improvement which comprises stopping addition of the aluminum salt before completion of reaction of the soap of the alkali metal while the reaction mixture has a pH in the range of 6 to 7, holding the reaction mixture at a pH in the range of 6 to 7 for at least a few minutes prior tofiltration, finally completing reaction of the fatty acid soap of the alkali metal a with added aluminum salt to give the resulting reaction mixture product a pH below 5, whereupon said product is filtered within a sufiiciently short period to avoid substantial hydrolysis.

6. A two-stage operation for preparing a hydrocarbon thickener which is a basic aluminum disoap of a C to C fatty acid which comprises reacting an amount of an aluminum compound with an alkali metal soap of a fatty acid in a first stage to form an unfinished reaction mixture product containing basic aluminum disoap of the fatty acid at a pH above 5, interrupting the reaction and holding the unfinished reaction mixture product for at least a few minutes at a pH above 5, thereafter completing the reaction of the unfinished reaction mixture product by addition thereto of a final relatively smaller amount of said aluminum compound that gives said reaction mixture produce a pH below 5 whereupon the disoap product is directly separated from acidic mother liquor of the reaction mixture product.

7. In the two-stage process as described in claim 6, in which the second stage completion of the reaction is carried out in a second reaction zone on a portion of the material produced by the first stage in a first reaction zone to form an amount of completely reacted product which can be quickly filtered.

8. A two-stage process for preparing a basic aluminum disoap useful as a hydrocarbon oil thickener, which comprises forming an aqueous solution of an alkali soap of a C to C aliphatic carboxylic acid to have a pH above 5, adding to said solution an aqueous solution of an aluminum salt to bring about the formation of basic disoap in the resulting reaction mixture, then, as the pH of the reaction mixture containing basic disoap tends to fall below 5, adding alkali to maintain the pH of the reaction mixture at a pH above 5, holding the reaction mixture at a pH above 5 for at least a few minutes and thereafter adding the final amount of aluminum salt to the reaction mixture and separating the disoap from the mother liquor which is at a pH below 5.

9. A process as defined in claim 8, wherein said alkali soap is a soap of sodium and the aluminum salt is aluminum sulfate.

References Cited in the file of this patent UNITED STATES PATENTS 2,350,688 Licata et al June 6, 1944 2,517,071 Gebhart et al Mar. 11, 1947 2,420,233 Edwards May 6, 1947 2,626,897 Young et a1 Jan. 27, 1953 

1. IN THE PROCESS OF MAKING A WATER-INSOLUBLE BASIC ALUMINUM DISOAP THAT THICKENS A HYDROCARBON OIL, THE IMPROVEMENT WHICH COMPRISES FORMING THE ALUMINUM DISOAP TO AN INCOMPLETE STAGE IN A LIQUID AQUEOUS MEDIUM AT BELOW 95% COMPLETION OF REACTION, THEN HOLDING SAID DISOAP IN THE AQUEOUS LIQUID MEDIUM KEPT AT A PH ABOVE 5 TO MINIMIZE DECOMPOSITION WHICH THE DISOAP UNDERGOES IN THE MEDIUM WHEN IT IS MORE ACIDIC, AND HOLDING THE DISOAP IN THE LIQUID MEDIUM AT A PH ABOVE 5 FOR AT LEAST A FEW MINUTES PRIOR TO COMPLETION OF REACTION THROUGH FINAL ADDITION OF ALUMINUM SALT WHICH IS REACTED TO FORM THE DISOAP AND GIVES SAID MEDIUM A PH BELOW 5 ON COMPLETION OF THE REACTION. 